I've heard from an ex-fundamentalist that for some people, conversion is a high in itself (I don't know if this is mostly true for Christians, or applies to movements in general. In any case, he said the high lasts for about two years, and then wears off, so that those people then convert to something else.
It has been claimed on this site that the fundamental question of rationality is "What do you believe, and why do you believe it?".
A good question it is, but I claim there is another of equal importance. I ask you, Less Wrong...
What are you doing?
And why are you doing it?